The present invention relates to a method for combined transfer-turnover of packets of cigarettes.
In cigarette manufacturing and conditioning systems, finished cellophaned packets, i.e. enclosed in an outer wrapping impermeable to air, are fed successively by a conveyor in a first direction with a first given orientation, and are then turned over to assume a second orientation normally rotated 90.degree. with respect to the first.
The packets are normally turned over by means of a turnover wheel rotating about a respective axis perpendicular to said first direction, and having a number of substantially radial arms, which move past the output end of the conveyor to receive respective packets and feed them forward with a second orientation rotated 90.degree. with respect to the first.
As they are turned over, the packets must of course be guided by outer guide elements, along which a whole face of each packet slides.
Due to the increasingly high output speed at which modern systems are operated, the sliding movement of the packets may result in scoring of the outer wrapping, which, being made of increasingly thinner sheet material for environmental reasons, is normally less resistant to external stress than formerly.
U.S. Pat. No. 3,894,626 and the description entitled "Vacuum Conveyor Sucks Up Cartons" (MACHINE DESIGN--vol. 46, no. 2, Jan. 24, 1974. pages 40-40, XP002067430), show a conveying device for combined transfer-turnover of products, wherein the products are fed successively by a first conveyor in a first direction perpendicular to a front face of each product and along a portion of a path extending through a transfer station, at which each packet is engaged, at its front face, by a second suction conveyor removing the product from the transfer station in a second direction parallel to the noted front face.
The aforementioned second suction conveyor comprises a porous conveying surface movable over and along a vacuum chamber having a plurality of holes; and air drawn through the porous conveying surface by the vacuum chamber holds the front faces of the products in contact with the conveying surface of the second suction conveyor.
Since only a relatively small part of the aforementioned porous conveying surface is engaged by the front faces of the products, and a relatively great quantity of air is sucked into the suction chamber through the remaining part of the porous conveying surface, the vacuum within the suction chamber is, in general, relatively weak as is the suction force through the porous conveying surface.
The known devices described above cannot be used for conveying products which are to be conveyed at a relatively high speed, such as cigarette packets in a modern cigarette packer normally operating at a rate of 600 packets/minute, owing to the fact that high transport speeds involve high centrifugal and inertial forces which cannot be contrasted by a weak vacuum.